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Old 09-09-2015, 06:28 PM   #1
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Groco seacock

My AC seacock has some play on the handle before it starts to engage the actual valve. Like maybe 1/8". It's not a loose handle but the actual shaft has play.

Is that a bad sign? Am I gonna sink?

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Old 09-09-2015, 06:45 PM   #2
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I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
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Old 09-09-2015, 06:49 PM   #3
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I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.

Wow. Really. Wonder if my others are like that? I will go look.
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Old 09-09-2015, 06:58 PM   #4
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Groco seacock

Generator has same setup I think.

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Old 09-09-2015, 06:59 PM   #5
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Main engine inlet. Not a good pic. Seems to be a better setup with bolts?

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Old 09-09-2015, 07:06 PM   #6
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Quote:
Originally Posted by TDunn View Post
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
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Old 09-09-2015, 07:08 PM   #7
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Generator is also a ball valve on the thru-hull. You have an actual seacock on the main engine intake. I always wonder why builders install ball valves considering the thread mismatch. I guess it is to save a few bucks since a seacock costs 2-3 times what a ball valve costs. It is possible to mount a seacock without a thru-hull, although I always use one.
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Old 09-10-2015, 12:52 AM   #8
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Originally Posted by TDunn View Post
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine How To at pbase.com
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Old 09-10-2015, 07:00 AM   #9
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Tdunn is right, replace those with real seacocks next time you haul.
Another option would be to use a Groco flanged adapter between the thru-hull and ball valve.

Is there a backing block or are those mounted directly to the hull? If no backing blocks, add them.
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Old 09-10-2015, 07:41 AM   #10
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Tdunn is right, replace those with real seacocks next time you haul.
Another option would be to use a Groco flanged adapter between the thru-hull and ball valve.

Is there a backing block or are those mounted directly to the hull? If no backing blocks, add them.

I think directly to the hull.

This looks like an interesting product.
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So if your valve wears out you just screw another one on.

I'm surprised the manufacturer didn't install the better seacocks on this boat for all through hulls. Why would they use them on the main engine inlet but not the gen or AC?
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Old 09-10-2015, 07:57 AM   #11
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Quote:
Originally Posted by TDunn View Post
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
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Generator is also a ball valve on the thru-hull. You have an actual seacock on the main engine intake. I always wonder why builders install ball valves considering the thread mismatch. I guess it is to save a few bucks since a seacock costs 2-3 times what a ball valve costs. It is possible to mount a seacock without a thru-hull, although I always use one.

Before the sky actually falls...

I did have some previous discussion with Buck Algonquin about the threads on their seacocks and ball valves... and their tech told me they purposely cut the leading threads so their NPT ball valves will attach securely to an NPS thru hull. Groco literature, somewhere down in the fine print, suggests the same.

Near as I can remember, I've never owned a boat with flanged seacocks. None have sunk, or even leaked.

Not suggesting this is good practice, just adding perspective...

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Old 09-10-2015, 09:10 AM   #12
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That first picture is of a marine ball valve. See the drain plug in the lower right- that indicates a marine thru hull ball valve. These valves have straight threads on the bottom to screw in to the straight pipe thread on the thru hull and tapered threads on the top.

As the pbase article indicates this installation isn't the best, integral flanged seacocks are better. But as the previous poster indicated, they rarely fail.

That slop that you feel is normal. There is a stem that fits in to the ball with a socket. It is designed to have a little slop.

David
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Old 09-10-2015, 09:15 AM   #13
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Groco seacock

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That first picture is of a marine ball valve. See the drain plug in the lower right- that indicates a marine thru hull ball valve. These valves have straight threads on the bottom to screw in to the straight pipe thread on the thru hull and tapered threads on the top. There is nothing wrong with these, but integral flanged seacocks are stronger.

That slop that you feel is normal. There is a stem that fits in to the ball with a socket. It is designed to have a little slop.

David

Oh. Cool. So not tapered and about to fall off or whatever?

How long do valves like this usually last? And why is the main seacock bonded but not these ball valves?

This makes me think these were added later by a yard and not the factory.
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Old 09-10-2015, 09:17 AM   #14
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Before the sky actually falls...

I did have some previous discussion with Buck Algonquin about the threads on their seacocks and ball valves... and their tech told me they purposely cut the leading threads so their NPT ball valves will attach securely to an NPS thru hull. Groco literature, somewhere down in the fine print, suggests the same.

Near as I can remember, I've never owned a boat with flanged seacocks. None have sunk, or even leaked.

Not suggesting this is good practice, just adding perspective...

-Chris
Yep and hundred's if not thousands of center console boats have that setup and are fine, it's not right but i don't see it as an immediate risk. The Nordhavn has flanged sea cocks, my dusky doesn't as seen far worse abuse and is all fine.
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Old 09-10-2015, 10:04 AM   #15
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According to the technical data sheets at Groco, Buck Algonquin and Apollo their ball valves all have only tapered threads although you can order apollo valves with straight threads. However, if you order straight thread valves, then you have the problem of finding straight thread hose barbs. While those may exist, Groco, Apollo and Buck Algonquin don't sell them.

So if some Buck Algonquin phone guy told you their valves have straight threads on the input end all I can say is that their technical specifications on the web site say the valves are all 100% tapered (NPT) threads.

Even if you can find hybrid thread valves, I would argue that real seacocks are stronger than ball valves every time. Why go with anything but the best?

As I said above, the only reason for a builder to put ball valves onto thru-hulls is to save money. Boat building is a low margin business, so saving $100 per thru-hull adds up. Nevertheless, I would demand actual seacocks.

When I bought my boat the thru-hulls all had ball valves. One of the first things I did before the boat went in the water was to replace all the thru-hulls and valves with seacocks. The original raw water intake on Tortuga had 17 separate plumbing fittings.
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Old 09-10-2015, 10:39 AM   #16
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Ok. I guess I will add this to my project list. 😢

When I change over to actual seacocks should they be bonded? The main engine (probably factory installed) seacock is tied to the binding system.
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Old 09-10-2015, 11:00 AM   #17
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"These valves have straight threads on the bottom to screw in to the straight pipe thread on the thru hull and tapered threads on the top."
Sorry Dave, that's incorrect. Both sides have tapered pipe threads. That's why Groco invented the Flanged Adapter.


"Near as I can remember, I've never owned a boat with flanged seacocks. None have sunk, or even leaked."
Chris, it is actually approved by ABYC to install ball valves directly onto thru-hull fittings because very few of them fail, but some do fail. Over the years I've sold thousands of ball valves and thru-hull fittings. I've only heard of one failure and that was when someone accidentally kicked one and the thru-hull broke below the valve.


Boat builders install them because it is cheap. It is not best practice by any means.

The miss-matched threads are not the only problem. The thru-hulls are very thin at the bottom of the thread and can break. It really doesn't cost much more to do it right. Why not do it right?

Yes they should be bonded. That's another problem with the ball valve on thru-hull, no easy way to connect a wire.

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Old 09-10-2015, 11:09 AM   #18
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Good information, straight thread VS. NPT thread.
I wonder what the cost difference would be between a through hull straight thread fitting and ball valve and a true sea cock would be? I would guess this affects the bottom line and that's why boat builders use them?
I would add that a flanged sea cock without the mechanical screw joint would be stronger. Most failures I have seen with mechanical joints occur at the cut in the threads. One less joint to worry about. I would recommend that you exercise the valve at least twice a year. Donít worry about the little play if it opens and closes properly. I would also ground it.
Ball valves , sea cock or straight are they best valves to use.
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Old 09-10-2015, 11:14 AM   #19
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So looking at these pictures, can I leave the existing through hull in place and just install the flange and a new valve?

How does that flange bolt to the hull?
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Old 09-10-2015, 11:41 AM   #20
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So if some Buck Algonquin phone guy told you their valves have straight threads on the input end all I can say is that their technical specifications on the web site say the valves are all 100% tapered (NPT) threads.

It was during a phone conversation, where I had asked pretty much the same questions... and partly because of the specs on their website.

He didn't say their valves have straight threads, though; he said their NPS thru-hull threads are "slightly modified" to work better with NPT ball valves. (Backwards from the way I said it before; sorry, just re-read my notes from back then.)

This from a note I posted (on another forum) shortly afterwards (11/7/2011):
Another tidbit I just learned today...

The very helpful sales assistant at Buck Algonquin told me they've machined the NPS threads on their thru-hulls in a way that allows them to accept an NPT-threaded ball valve. He said to expect approximately 3 turns before the threads lock up, with Teflon tape recommended as the pipe sealer.

He also said he thinks all thru-hull manufacturers do the same -- and that seems to jive with what Groco describes as "combination threads" on the ends of their NPS-threaded through-hulls.
At the time I thought it made absolutely no sense at all for companies to make ball valves with NPT threads intended to mate up with NPS thru-hulls. Since then I've come to suspect they assume their marine ball valves will be used in a number of different applications where NPT threads would be appropriate... and have maybe adopted this kind of approach simply because ONE of those applications (probably relatively low volume, marine thru-hulls) would mean mating NPT-NPS threads. IOW, cost control for the manufacturers, too, not just the boat builders.


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